Comparative analysis of the performance of hydrocarbon refrigerants with R22 in a sub-cooling heat exchanger refrigeration system

In this study, the performance of some hydrocarbon refrigerants (R290, R600a and R1270) as alternatives to R22 in vapour compression refrigeration system was investigated theoretically employing a sub-cooling heat exchanger. The effects of sub-cooling on the performance of the investigated refrigerants were quantified in terms of relative capacity index. The results obtained showed that the saturated vapour pressure and specific volume of R290 and R1270 are very close to those of R22; therefore, they could be used as substitutes for R22. The condenser duty using R290, R600a and R1270 are better than that of R22 with the highest value obtained using R1270, which shows that they could perform very well as refrigerants in heat pump systems. The coefficient of performances of all the investigated refrigerants were found to be in the range 3.10–3.51. The degree of sub-cooling greatly increased the coefficient of performance and it had positive effects on the refrigerating capacity. The average relative capacity indices obtained for R290, R600a and R1270 were 35.4%, 29.5% and 27.3% higher than that of R22, respectively. Generally, the thermophysical properties of R290 and R1270 matched those of R22 and the two refrigerants exhibited better performance than R22 in sub-cooling heat exchanger refrigeration system. R600a has slightly better performance in terms of lower power per ton of refrigeration and higher coefficient of performance, but its saturation pressure and specific volume deviate significantly from that of R22, which will require major system redesign before it can be employed as R22 substitute.